A crude oil or a natural gas condensate contains a mercury component in the broad range of 2 to 5,000 wtppb in forms of elemental mercury, ionic mercury, or organic mercury.
In a liquid hydrocarbon such as a crude oil, mercury exists in forms of “elemental mercury”, “ionic mercury”, or “organic mercury”; herein, mercury in these three forms is generally defined as a “mercury component”, and “ionic mercury” and “organic mercury” are defined as a “mercury compound”.
A mercury component contained in crude oil has various adverse effects of eroding aluminum devices, poisoning catalysts, or deteriorating ambient environment, so it is occasionally necessary to remove this mercury component as much as possible.
As a removal method for the mercury component contained in crude oil, there is the method disclosed in patent document 1 (Japanese Patent No. 2630732).
This removal method in patent document 1 brings a raw liquid hydrocarbon into contact with a catalyst, thereby converting the mercury component contained therein into elemental mercury, and thereafter distilling the liquid hydrocarbon so as to be separated into two fractions or more. The fraction whose elemental mercury content is low is used as a product, while the fraction whose elemental mercury content is high is processed by adsorption, thereby removing the elemental mercury.
However, in patent document 1, there is the problem in that the expenses are increased because of the cost of the devices such as a distillation column which distills liquid hydrocarbon. Also, there is the problem in that an adsorption process occasionally becomes difficult because there is a high risk that the fraction becomes contaminated with components which greatly inhibit adsorption in the case that fractions obtained by distillation is processed by adsorption.
Patent document 1: Japanese Patent No. 2630732